Conventionally, secondary batteries with wound electrode bodies formed by winding elongated positive and negative electrode plates with an elongated separator interposed therebetween are known. The positive electrode plate therein is formed by an elongated positive electrode collector foil with a positive electrode active material layer formed in part thereof, and thus includes a longitudinally extending strip-shaped positive electrode portion where the positive electrode active material layer is provided, and a longitudinally extending strip-shaped positive electrode collector portion where the positive electrode active material layer is not provided. The negative electrode plate is formed by an elongated negative electrode collector foil with a negative electrode active material layer formed in part thereof, and thus includes a longitudinally extending strip-shaped negative electrode portion where the negative electrode active material layer is provided, and a longitudinally extending strip-shaped negative electrode collector portion where the negative electrode active material layer is not provided. In a wound electrode body configuration, the positive electrode collector portion of the positive electrode plate protrudes from the separator in a spiral shape on one side in the axial direction thereof, while the negative electrode collector portion of the negative electrode plate protrudes from the separator in a spiral shape on the other side in the axial direction thereof.
It is also known to provide an insulating layer made of resin or the like to the collector portions and others of the positive and negative electrode plates in secondary batteries having the above mentioned configuration. For example, Patent Literatures 1 and 2 mentioned below disclose a secondary battery having such an insulating layer provided therein.
The secondary battery disclosed in Patent Literature 1 includes a cylindrical wound electrode body formed by winding positive and negative electrode plates with a separator interposed therebetween into a cylindrical shape (see FIG. 1 and others of Patent Literature 1). In this secondary battery, a resin coating is applied to the positive and negative electrode plates near the boundary between active material coated portions (positive and negative electrode portions) and exposed portions (positive and negative electrode collector portions) to form strips of insulating layers extending from one end to the other in a longitudinal direction of the positive electrode plate and others (from an innermost end to an outermost end in the cylindrical wound electrode body configuration). It is stated that providing such an insulating layer allegedly covers an edge of the active material layer formed in the active material coated portion adjacent to the exposed portion, whereby this edge of the active material layer can be prevented from coming off of the collector foil, and a short circuit resulting from fallen fragments of the active material layer can be prevented.
The secondary battery disclosed in Patent Literature 2 includes a cylindrical wound electrode body formed by winding positive and negative electrode plates with a separator interposed therebetween into a cylindrical shape (see FIGS. 1, 2, and others of Patent Literature 2). In this secondary battery, insulating resin is coated or an insulating tape is affixed to the positive and negative electrode plates in part of the collector exposed portions (positive and negative collector portions) on the side of the active material coated ends (positive and negative electrode portions) to form strips of insulating layers extending from one end to the other in a longitudinal direction of the positive electrode plate and others (from an innermost end to an outermost end in the cylindrical wound electrode body configuration). It is stated that providing such an insulating layer allegedly reinforces the collector exposed portions whereby deformation thereof caused by vibration or impact can be prevented.